Approximately 27,000 deaths occur annually in the United States alone from patients with end-stage liver disease. With an aging population, this number is only expected to increase. The current definitive treatment is orthotropic transplantation. However, due to high demand there exists a critical shortage of donor livers. Those patients fortunate enough to receive a transplant are burdened with the risk of chronic rejection and the morbidity associated with a lifelong regimen of immunosuppressant therapy. This treatment is especially difficult for elderly patients. This application addresses a regenerative medicine strategy for engineering an implantable liver graft for patients with end-stage liver failure. It is based upon three fundamental concepts: 1) the native ECM of the liver, including the three dimensional untrastructure and composition, represents an ideal and required substrate for liver regeneration, 2) whole liver ECM scaffolds retain the three-dimensional macrostructure, the native microvascular network, and the bile drainage system; allowing for complete recellularization of all native cell types, and 3) liver regeneration can be promoted when reseeded whole liver ECM grafts are placed in the appropriate three dimensional microenvironment; specifically, in-situ in patients with liver failure. The objectives f the proposed research are to (1) establish an effective method for reseeding a three- dimensional liver scaffold, with a focus on systematically seeding both parenchymal and non parenchymal cells in their native location and to (2) evaluate the host response to the implantation of a reseeded three- dimensional liver scaffold. Additionally, the methods and techniques developed in this study present an important step towards the establishment of decellularization and recellularization criteria necessary to successful produce the first fully functional bioengineered livers for organ transplantation and drug discovery. PUBLIC HEALTH RELEVANCE: This project directly addresses the public health issue of a severe shortage of donor organs for patients awaiting transplantation. The methods and techniques developed in this study present a critical step towards the development of a fully functional liver graft. The findings of this project will serve as the foundation for future avenue of investigation that will aim to create functional liver tissue for patients with end-stage liver disease, eliminating the need for liver transplantation and paving the way for whole organ engineering.